Biaxially stretch-blow-molded containers of a thermoplastic polyester such as polyethylene terephthalate (PET) have excellent transparence, surface luster as well as shock resistance, rigidity and gas-barrier property necessary for the bottles, and have been widely used as bottles for containing various kinds of liquids.
In producing bottled products, in general, the contents are hot-filled, or the contents are filled and are, thereafter, heat-sterilized or pasteurized to improve the preservability of the contents. However, the polyester bottles have a defect of poor heat resistance undergoing thermal deformation and volume-contracting deformation at the time when the contents are hot-filled. Therefore, it is a practice to further heat-set the biaxially stretch-blow-molded containers.
In the use (heat- and pressure-resistant bottle) in which a content that spontaneously produces pressure is heat-sterilized or pasteurized after it has been filled and sealed, however, pressure and heat act simultaneously onto the bottom portion of the bottle causing the bottle portion to be swollen due to the heat-creeping phenomenon. Therefore, attempts have been made to more increase the thickness of the bottom portion than that of the ordinary pressure-resistant bottles so as to impart heat resistance thereto over the limited area, which, however, is not still sufficient making it difficult to attain the effort for reducing the weight and decreasing the thickness.
From the above points of view, there have been proposed a heat- and pressure-resistant polyester bottle and a process for producing the same. For example, JP-A-8-267549 and JP-A-9-118322 filed by the present applicant are proposing heat- and pressure-resistant polyester bottles produced by a 2-stage blow-molding method and processes for producing the same. According to these processes, there can be provided polyester bottles having excellent resistance against the heat and pressure free of the above-mentioned problems even by effecting the heat-sterilization or pasteurization.
Since it has been made possible to provide the polyester bottles having excellent resistance against the heat and pressure, it is now desired to use the polyester bottles for containing beverages that spontaneously produce pressure and that must be heat-sterilized or pasteurized after filled like beer and the like.
That is, though beer has heretofore been traditionally contained in a glass bottle or a can, it has now been desired to contain beer in a biaxially stretch-blow-molded bottle of polyester which is light in weight having excellent shock resistance, as one form of container for packing beer.
When it comes to beer, on the other hand, a general and familiar container of beer is a glass bottle having a neck portion of a slender shape, i.e., having the shape a so-called crane neck of which the diameter in cross section is smaller than that of the body portion but which is long. It is, therefore, desired that the polyester bottle, too, has the shape of the so-called crane neck with a long neck portion as it is the familiar shape of beer bottles.